feat(highway): render caged + guideTones teaching labels (§6.6) (#545)

Mirror the voicing/fn.rn teaching-mark render for the two new chord-template
fields, in both the 2D and 3D highways:

- Extend the shared pure chordHarmonyLabels() helper (identical in static/highway.js
  and plugins/highway_3d/screen.js) to also surface caged ("CAGED: E") and
  guideTones ("gt 4,10"), pre-formatted and node-testable. Invalid caged enum and
  out-of-range / non-int guide tones are filtered out.
- Draw both, stacked above the existing rn/voicing labels, in distinct colors.
- Gated behind the SAME teaching-marks toggle (_showTeachingMarks 2D /
  teachingMarksVisible 3D) — no clutter on the default highway.

Render only — no scoring / NoteVerifier coupling.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/js/highway_chord_harmony.test.js

@@ -29,21 +29,42 @@ const labels2D = loadFn('static/highway.js', 'chordHarmonyLabels');
 const labels3D = loadFn('plugins/highway_3d/screen.js', 'chordHarmonyLabels');
 
 for (const [name, fn] of [['2D', labels2D], ['3D', labels3D]]) {
-    test(`chordHarmonyLabels (${name}) surfaces rn + voicing`, () => {
-        assert.deepEqual(fn({ rn: 'ii7', q: 'm7', deg: 2 }, 'open'),
-            { rn: 'ii7', voicing: 'open' });
+    test(`chordHarmonyLabels (${name}) surfaces rn + voicing + caged + guideTones`, () => {
+        assert.deepEqual(fn({ rn: 'ii7', q: 'm7', deg: 2 }, 'open', 'E', [4, 10]),
+            { rn: 'ii7', voicing: 'open', caged: 'CAGED: E', guideTones: 'gt 4,10' });
     });
 
     test(`chordHarmonyLabels (${name}) trims whitespace`, () => {
-        assert.deepEqual(fn({ rn: '  V7 ' }, '  drop2 '),
-            { rn: 'V7', voicing: 'drop2' });
+        assert.deepEqual(fn({ rn: '  V7 ' }, '  drop2 ', '  G  ', []),
+            { rn: 'V7', voicing: 'drop2', caged: 'CAGED: G', guideTones: '' });
     });
 
     test(`chordHarmonyLabels (${name}) empties absent / malformed inputs`, () => {
-        assert.deepEqual(fn(null, undefined), { rn: '', voicing: '' });
-        assert.deepEqual(fn({}, ''), { rn: '', voicing: '' });
-        assert.deepEqual(fn({ rn: 7 }, 7), { rn: '', voicing: '' });   // non-string
-        assert.deepEqual(fn(undefined, 'shell'), { rn: '', voicing: 'shell' });
-        assert.deepEqual(fn({ rn: 'vi' }, null), { rn: 'vi', voicing: '' });
+        assert.deepEqual(fn(null, undefined),
+            { rn: '', voicing: '', caged: '', guideTones: '' });
+        assert.deepEqual(fn({}, ''),
+            { rn: '', voicing: '', caged: '', guideTones: '' });
+        assert.deepEqual(fn({ rn: 7 }, 7),   // non-string
+            { rn: '', voicing: '', caged: '', guideTones: '' });
+        assert.deepEqual(fn(undefined, 'shell'),
+            { rn: '', voicing: 'shell', caged: '', guideTones: '' });
+        assert.deepEqual(fn({ rn: 'vi' }, null),
+            { rn: 'vi', voicing: '', caged: '', guideTones: '' });
+    });
+
+    test(`chordHarmonyLabels (${name}) rejects invalid caged enum`, () => {
+        assert.equal(fn(null, null, 'X').caged, '');        // not a CAGED letter
+        assert.equal(fn(null, null, 'e').caged, '');        // lower-case rejected
+        assert.equal(fn(null, null, 7).caged, '');          // non-string
+        assert.equal(fn(null, null, ['E']).caged, '');      // non-string
+        assert.equal(fn(null, null, 'C').caged, 'CAGED: C');
+    });
+
+    test(`chordHarmonyLabels (${name}) filters out-of-range / non-int guide tones`, () => {
+        assert.equal(fn(null, null, '', [12, -1, 3, 'x', 10]).guideTones, 'gt 3,10');
+        assert.equal(fn(null, null, '', [0, 11]).guideTones, 'gt 0,11');  // boundaries kept
+        assert.equal(fn(null, null, '', []).guideTones, '');
+        assert.equal(fn(null, null, '', '4,10').guideTones, '');          // non-array
+        assert.equal(fn(null, null, '', [12, -1]).guideTones, '');        // all dropped
     });
 }